Typically, compression candles are made from wax that has been formed into prills, which prills are compressed in a mold to make a candle. The candle industry has traditionally relied on prilled paraffin waxes to make compression candles.
Some attempts to formulate waxes from bio-based, renewable materials suitable for making compression candles have suffered from a variety of problems, including poor compressive strength, poor cohesive strength, slump at elevated temps, flashing, tooling, and fat bloom associated with triglycerides. The term cohesive strength is used herein to refer to the bulk strength of a compressed wax article (i.e., load to failure of a test specimen).
A desirable characteristic for prilled waxes is to compress evenly in the compression mold and for the resulting compressed wax article to exhibit sufficient strength to resist chipping or crumbling when subjected to rough handling or dropping. Natural oil-based waxes may be mixed with paraffin wax to create hybrid waxes with improved properties. However, hybrid waxes with greater than 50% weight natural oil-based wax, when compressed, typically fail to exhibit bulk strengths that are comparable to paraffin systems. Consequently, the resulting candles are more susceptible to damage during processing and handling. They can also be more susceptible to damage while being ejected from the compression mold, resulting in defects such as surface scarring, erosion, pitting and/or filming. The strength issues become more problematic as the size of the candle that is being manufactured increases. For example, it is particularly challenging to make bio-based compression candles that are freestanding and/or that are larger than about 2.5 inches wide by about 2.5 inches tall.
While paraffin-based compression candles exhibit good strength properties, paraffin wax does have some disadvantages, such as being a non-renewable resource; exhibiting visible emissions; and having a low fragrance holding ability (about 1% maximum by weight) in freestanding and/or larger-size compression candles.
Hence, there is continuing interest in the development of new wax compositions and candle products based on bio-based materials, such as natural oils, that have a high compressive and a high cohesive strength.